Harbin Water Supply and Drainage Group Co., Ltd. and Heilongjiang Electric Power Development Company are tackling the pressing issue of pollution caused by power electronic devices and other harmonic sources. Two fundamental approaches have been proposed by Hou Yannan and Ji Wenbo to address this challenge. The first involves modifying both the power plant and the devices themselves to generate fewer harmonics, aiming to improve the power factor and reduce environmental impact. The second approach includes installing harmonic compensation equipment to mitigate harmonic distortions, which is particularly beneficial given the variety of harmonic sources present. Traditionally, harmonic compensation has relied on passive filters, which consist of reactors and capacitors connected in series. However, these passive filters suffer from large physical dimensions and limited filtering effectiveness. Recently, active power filters utilizing advanced semiconductor components have gained significant attention due to their superior performance.
An active power filter operates based on two main components: a harmonic and reactive current detection circuit and a compensation current generation circuit. Its core principle lies in detecting the distorted currents and calculating the necessary compensation signals using specialized detection circuits. These signals are then amplified and converted into compensation currents by the generation circuit. When combined with the load current, these compensation currents neutralize the harmonics and reactive power issues, resulting in a more efficient and cleaner power supply. Active power filters represent a novel power electronic solution capable of dynamically adapting to varying harmonic frequencies and reactive power demands.
Two key advancements have significantly enhanced the efficacy of active power filters. First, the advent of high-power switching devices, such as high-voltage Insulated Gate Bipolar Transistors (IGBTs), has enabled the production of robust and efficient inverters capable of handling large currents. Second, the instantaneous reactive power theory introduced by H. Akagi et al. at the University of Science and Technology in China has provided a solid theoretical foundation for real-time harmonic detection in three-phase systems. This theory supports the use of voltage-source inverters with a modular design, facilitating the development of more effective compensation strategies.
Research efforts at companies like Aiyuan Power Filter have focused on refining both parallel and series configurations of active power filters. By integrating elements such as pole rectifier bridges, filter capacitors, and boost chopper circuits, engineers have achieved greater efficiency and reliability. Control mechanisms involving precise timing and switching of power semiconductors ensure that AC currents remain sinusoidal, thus improving the overall power factor and minimizing losses.
The ongoing development of active power filters continues to emphasize cost reduction, enhanced device performance, and improved system efficiency. As medium and high-power electronic devices become increasingly prevalent within the power grid, the demand for efficient source power factor correction solutions grows. Key areas of focus include optimizing control strategies for single-phase and three-phase systems, exploring advanced techniques like decoupling and fuzzy logic control, and leveraging high-frequency switching to minimize harmonic distortion. In essence, active power filters not only contribute to cleaner energy but also hold immense potential for future technological innovation in the field of power electronics.
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